Valve device for lung ventilator



Aug 12, 1958 sis. ANDREASEN 2,347,001

' VALVE, DEVICE FOR LUNG VENTILATOR 7 Filed A ril 27. 1956 IN YEA 7 M g ,8. 514m f/m KW A TTURNE Y United States atent 2,847,001 VALVE Device son LUNG VENTILATOR Christian B. Andreasen, Elkins Park, Pa., assignor to Air- 'Shields, Ina, Bucks County, Pa., a corporation of Delaware Application April 27, 1956, Serial No. 581,202 4 Claims. (Cl. 128-29) This invention relates to apparatus for use with anesthesia machines and is particularly concerned with an automatic control valve for the anesthesia gas system.

Anesthesia machines are generally equipped with a breathing bag by means of which the operator may assist in supplying gas to the patients lungs by applying pressure to the breathing bag during the inhaling period. In my ctr-pending application No. 485,229, filed January 35, 1955, apparatus is disclosed for applying both positive and negative phases of the breathing cycle to the breathing bag, thereby assisting the patient in a more effective manner than has heretofore been accomplished. The generation of anesthesia gas in the anesthesia machine circuit is sometimes at a rate slightly higher than that at which the patient uses the anesthesia gas.

Under these circumstances the anesthesia system fills up including the breathing bag which becomes over distended and therefore will not respond properly to the negative phase of the breathing cycle which assists in withdrawing the gas from the patients lungs. When overdistention occurs, whether used with automatic equipment or with the manually operated breathing bag, it has been necessary to relieve the volume of gas in the anesthesia circuit by opening a valve to bleed olf some of the gas to permit partial deflation of the breathing bag.

It is a primary object of the present invention to provide an automatic bleed valve for reducing the volume of the anesthesia gas in the anesthesia machine circuit when the breathing bag becomes over distended.

Another object of the invention is the provision of c. simple valve construction for relieving excess anesthesia gas from the anesthesia circuit to the breathing bag actuating air system upon thedevelopment of a predetermined negative pressure diiferential between the two gas systems.

How the above and other objects and advantages are attained will be clear from the following description of the figures in which Figure 1 is an elevational view, partly in section showing the breathing bag portion of the anesthesia machine circuit and the variable pressure chamber in which the breathing bag is mounted for automatic actuation.

Figure 2 is an enlarged sectional elevation of the mounting of the breathing bag and its connection to the anesthesia machine circuit including the valve structure of the present invention.

Referring to the figures it will be seen that the normal breathing bag 5 of the anesthesia machine is shown connected into the flexible tube 6 which leads to the anesthesia circuit and the patients lungs. A manual valve 7 connects the breathing bag 5 into the line 6, valve 7 being of the two-way variety which provides for either connecting breathing bag 5 to tube 6, or for shutting off the connection from bag 5 to tube 6 and connecting tube '6 to tube 3 which leads to the automatic ventilator equipment. A second breathing bag 9 is supported in a variable pressure chamber 1t) ice which is preferably constructed of transparent material to permit the operator to observe the motions of breathing bag while the ventilator is in operation. Breathing bag 9 is connected to tube 11 which in turn connects to the passage 8 leading to delivery tube 6 when valve 7 is in proper position.

Connected to chamber 10 is a bellows device 12 which is moved by suitable mechanism (not shown) connected to rod 13. By properly timing the compression stroke of bellows 12 the length of application of positive pressure in chamber 111 is suitably determined to provide the inhalation action in the anesthesia gas contained in bag 9 and the circuit. The maximum positive pressure in chamber 10 is controlled by the relief valve 14 which releases the gas in chamber 10 when it exceeds a predetermined value for which valve 14 is set. Valve 14 is preferably adjustable to permit selection of the desired maximum value to the particular pressure needed for any condition of operation.

Likewise the expansion stroke of bellows 12 produces the negative pressure required in chamber 10 to transmit the negative phase to the bag 9 and thus to the anesthesia gas in ducts 8 and 6. Valve 15 connected to the chamber 1% provides for maintaining the proper value of negative pressure during the expansion stroke. The time of application of the negative pressure to the system is controlled by suitable timing mechanism for the driving system which controls the length of time for the downward stroke of bellows 12.

in the anesthesia machine circuit anesthesia gas is usually generated at a rate slightly in excess of the rate at which it is used by the patient. Thus the gas accumulates in the circuit and eventually the breathing bag 59 becomes filled to the extent that at the end of the pressure phase it is only partly collapsed. Thus when the negative pressure develops in chamber 10 transmission of this negative pressure to the bag 9 causes full expansion of the bag before the negative phase is completed. When this occurred it has heretofore been necessary that the operator open a valve in the anesthesia system and bleed off some of the anethesia gas in order to reduce the volume to reestablish effective action of the breathing bag. With the improved ventilator construction of this invention means are provided for automatically correcting this overdistention.

At the juncture of breathing bag connecting tube 11 with the duct 8 an enlarged housing 16 is shown. Normally housing 16 contains a pressure gauge 17 which is mounted to close the top of the housing 16 and incorporates a dial which indicates to the operator the pressure of the gas in the anesthesia machine circuit. As is clearly shown in Figure 2, connecting tube 11 leads into a chamber 18 which connects to the main chamber 19, and the duct 8. Thus a free passageway is provided between breathing bag 9 and duct 8.

Mounted in the lower portion of chamber 19 according to the present construction there is an annular ring 25) supported by two or more tubes 21. Tubes 21 lead from the chamber 19 to the upper side of ring 21 A dished cover 22 is attached to the outer surface of the ring 26 and thus forms a small chamber 23 into which the upper ends of tubes 21 lead. A disc 24 is supported on the inner edge of ring 2% and is held in position by its weight, thus forming a portion of the lower surface of small chamber 23.

With this construction the tubes 21 interconnect main chamber 10 and small chamber 23 thus providing the same pressure in 23 as in 10. During the positive pressure phase of the breathing cycle the pressure in chamber 10 will be positive and the pressure in bag 9 will be the same as in chamber 10. Therefore the pressure in chamhers 23 and 18 will be the same. Under these circumstances there is no communication between chamber 18 and chamber 23 since the valve disc 24 remains in position. to seal. During the negative phase of the breathing cycle the pressure in chamber 10 and breathing bag 9, under normal circumstances is also the same When the bag is being expanded. However, when the amount of gas in the anesthesia machine circuit becomes excessive and the bag 9 becomes over-distended on the negative phase, then bag 9 cannot be expanded further and the negative pressure in chamber 10 becomes lower than the negative pressure in bag 9. As a result the pressure in cham ber 23 is less than in chamber 18, and consequently the lid or disc 24 is liftedto permit withdrawal of gas from the bag 9 through chamber 23 and tubes 21 into chamber 10. This withdrawal of gas from the anesthesia machine circuit during the negative phase reduces the volume of gas therein and upon application of the positive phase of the cycle valve disc 24 closes and gas is forced from bag 9 into the anesthesia machine circuit through duct 8 thus causing at least partial collapsing of the bag 9. The proper negative pressure can be applied to it during the negative pressure phase developed in chamber 10 until the bag becomes fully expanded.

The negative difference at which bleed occurs from the breathing bag system to the variable pressure chamber 10 is accurately controlled by the valve device. For the proper action this diiference should be small, for example, of the order of -l cm. of water. In the present construction this difference is developed by providing the proper weight for the disc 24. The maximum negative pressure in variable pressure chamber 15) is controlled by relief valve 15 which may be set to provide a suitable operating value, such as -10 ems. water. Under normal operation extremely close values of negative pressure are maintained inside and outside bag 9. In view of the small pressure difference (1 cm. H O) as compared to the maximum or normal negative operating pressure (e. g.

' 10 cms. H O) the bleed action is immediately effective when needed since only about 10% pressure difference is needed to produce the bleeding action. Only a portion of the dwell of the negative phase is required to return the pressure in bag 9 to that of chamber 10. This is because bleeding will occur from bag 9 to chamber 10 to take care of volume increase of chamber 10 near the end of the negative pressure phase when distention develops. Even during the bleeding action there is no appreciable effect on the negative pressure in the anesthesia machine because only a negligible pressure change occurs. Thus during the bleeding the pressure in the bag would be -9 ems. as compared to -l ems. water in the bellows chamber.

it will be understood that the external breathing bag 5 is for normal manual use directly by the operator, chiefly for emergency purposes in case of failure of power or malfunctioning in the ventilator system. In such an emergency, valve 7 is turned to shut off the ventilator system and to connect bag 5 to the tube 6 so that the operator may apply the normal manual breathing assist-- ance through the medium of bag 5. However when theventilator is functioning valve is turned so as to shut off bag 5 and connect bag 9 into the anesthesia system through duct 6. Application of the positive and negative phases of the breathing cycle to bag 9 induces improved breathing action in the lungs of the patient, the addition of the negative phase being of particular benefit to the patient in producing proper scavenging of the lungs and thus reducing the carbon dioxide concentrations in the blood during the period of anesthesia. When the volume of gas in the anesthesia machine system has become excessive so that on the negative phase breathing bag 9 becomes overdistended, valve 24 automatically opens as previously described in order to relieve the anesthesia machine circuit of some of its gas and thus reduce the volume to permit proper functioning of both the positive and negative phases of the breathing cycle in the venti- 4. lating machine. This action occurs automatically without the need for attention by the operator and thus keeps the volume of gas in the anethesia circuit properly stabilized to provide proper functioning of the ventilator system.

The use of a large diameter for the movable valve part has certain advantages. By having a large perimeter the valve need move only a slight amount to provide a relatively large area opening. Thus the flow velocity is kept low through the valve and inertia effects which would be produced by large and rapid valve movements are eliminated. By this construction a sensitive valve without flutter or chatter is provided. Also by having a larger valve with greater weight the desired accuracy of op eration may be obtained even with slight variations in valve weight. The same weight variation in a small valve will cause a relatively greater change in the valve operation.

From the foregoing it will be evident that my improved ventilator device provides simple and effective means for automatically bleeding the excessive anesthesia gas generated in the anesthesia machine circuit in a manner which eliminates the need for manual attention by the operator. This improved valve device provides an effective means for eliminating the problem of overdistentation in the breathing bag so that the ventilating apparatus is capable of continuously providing the proper cycle of positive and negative pressures to the anesthesia machine gas supplied to the patient.

I claim:

1. Lung ventilating apparatus having a breathing bag, a duct for connecting said bag to an anesthesia machine system, a chamber interconnecting said bag and said duct, a variable pressure chamber in which said breathing bag is supported, pressure varying means connected to said pressure chamber for providing alternate positive and negative pressure phases, a relief valve device mounted in said interconnecting chamber above the breathing bag, said device having an upper wall, side walls and a ring member forming a lower inturned flange, tubular members holding said device above the bottom of said interconnecting chamber, each of said members forming a channel between the upper side of said flange and said variable pressure chamber and a disc normally engaging said flange to form the movable portion of said valve device.

2. Lung ventilating apparatus having a variable pressure chamber, a variable volume device having flexible walls, the interior of said device being connected to the duct of an anesthesia machine system, said variable volume device being mounted with its flexible walls in association with said variable pressure chamber, pressure varying means connected to said chamber to develop alternate positive and negative pressure phases therein, a relief valve located between said variable volume device and said variable pressure chamber and incorporating a valve chamber having an upper surface and a lower surface with a valve opening therein, a movable valve member to close the opening, a lurality of tubular members supporting said valve chamber in position and conmeeting it with said variable pressure chamber, said relief valve being constructed to open and bleed gas from said device to said chamber when the negative pressure in said chamber falls below that in said device by a predetermined value.

' sure chamber for providing alternate positive and negative pressure phases therein, a relief valve device constructed to allow gas to bleed from said breathing bag and duct to said variable pressure chamber and to prevent gas from passing from said chamber to said duct, said relief valve device incorporating a disc member of suitable weight to control the opening of said device upon a predetermined difference in negative pressure between said variable pressure chamber and said breathing bag.

4. Lung ventilating apparatus having a breathing bag, a duct for connecting said bag to an anesthesia machine system, a variable pressure chamber in which said bag is mounted, pressure varying means connected to said pressure chamber for providing alternate positive and negative pressure phases therein, a relief valve device constructed to allow gas to bleed from said breathing bag 10 2,737,176

and duct to said variable pressure chamber and to prevent gas from passing from said chamber to said duct, said release valve device being constructed to open at a negative pressure difierence of approximately one centimeter of water.

References Cited in the file of this patent UNITED STATES PATENTS Blease Apr. 1, 1952 Fox Mar. 6, 1956 

